1. Field of the Invention
The invention relates to a wireless device and a bandwidth managing method thereof and, more particularly, to a Bluetooth device and a bandwidth managing method thereof.
2. Description of the Related Art
Bluetooth is a wireless communication technology used in a short distance and with a low cost, and it makes a communication in the frequency-hopping spread spectrum (FHSS) mode to reduce interruptions. Since the Bluetooth technology has these advantages, much wired electronic equipment has been developed to be wireless Bluetooth devices such as Bluetooth earphones, Bluetooth microphones, Bluetooth mousse and keyboards and so on in recent years. These Bluetooth devices can transmit information by radio wave among the electronic devices such as computers, mobile phones, personal digital assistants (PDA) and so on.
The Bluetooth technology transmits information between a master and a slave in a time division duplex (TDD) mode, and the data transmission rate can reach 1 Mbps. The Bluetooth technology supports two connecting types. One of them is asynchronous connectionless (ACL) channel, and another is synchronous connection oriented (SCO) channel. The ACL channel is used to transmit data or command, while the SCO channel is used to transmit sound. The master can transmits data to a plurality of slaves, and different master-slave pairs can use different connecting types, but the sum of the bandwidth still has a fixed upper limit.
FIG. 1 is a schematic diagram showing a conventional Bluetooth device. Please refer to FIG. 1. The master 10 is, for example, a mobile phone. The slave 20 is, for example, a Bluetooth earphone. In the conventional technology, before the sound is transmitted under the Bluetooth technology BT1.1, the SCO channel between the master 10 and the slave 20 is established at advance. Fixed slots for transmitting sound signals at fixed time and amount are reserved when the SCO channel is established. Each slot is 625 microsecond. When the master 10 transmits sound signals to the slave 20, the TX slot is used to transmit the sound signals to the slaves 20. On the contrary, when the slave 20 transmits sound signals to the master 10, RX slot is used to transmit the sound signals to the master 10. In other words, in the conventional technology, to avoid that the sound becomes on and off in the transmission, the SCO channel distributes TX slots and RX slots for transmitting sound signals at set intervals, and the TX slots and the RX slots appear in pairs, and the packet length thereof is the same. However, users do not continuously speak in an actual communication. That is, when no sound signal needs to be transmitted, the SCO channel still distributes TX slots and RX slots with fixed frequency for transmitting sound signals. Although the above method keeps a good communication quality, the transmission bandwidth is quietly wasted.
The specification after the Bluetooth technology BT 1.2 develops enhance synchronous connection oriented (ESCO) channel. After ESCO channel is established online, users can readjust the period when TX slots and the RX slots appear in pairs. However, the ESCO channel only can prolong the period to 254 slots. In other words, the TX slots and RX slots must appear once in about 0.15 seconds. In actual application, the bandwidth still will be wasted when no sound signal needs to be transmitted. In addition, the version of BT 1.2 can set the packet length of the TX slots and the RX slots to make the packet length asymmetrical, but the TX slots and the RX slots still must appear in pairs. That is, although two sides do not speak simultaneously, the ESCO channel also distributes the TX slots and the RX slots for transmitting the sound. Meanwhile, one the TX slots and the RX slots become unnecessarily wasted bandwidth. Even when neither of the two sides speaks, it is unnecessary and wastes bandwidth to distribute TX slots and RX slots for transmitting the sound.